Fabrics may be used in protective clothing such as bulletproof or bullet-resistant vests. The fabrics may be configured to absorb and/or distribute the impact of a projectile. Such fabric may include one or more layers. Each layer may include a plurality of yarns woven together. Each yarn may include a plurality of aramid and/or para-aramid fibers such as KEVLAR by E. I. du Pont de Nemours and Company or TWARON by Teijin Aramid. An aramid fiber may be understood as an aromatic polyamide whose chain molecules are highly oriented along a fiber axis. Para-aramids may have relatively much higher tenacity and elastic modulus than aramids and may provide outstanding strength to weight properties.
A fabric and yarns in the fabric subjected to ballistic impact may experience strains that depend on the ballistic impact. In a yarn, strain may be understood as a relative change in length. For example, the strain experienced by a particular yarn may depend, at least in part, on the location and/or orientation of the yarn relative to a point of ballistic impact as well as a travel direction, velocity and/or type of a ballistic projectile. It may therefore be desirable to detect strains in one or more yarns in a fabric subject to ballistic impact.